Serum laboratory studies showed unremarkable (complete blood count, routine chemistry test, clotting studies, electrolyte panel, creatinine, glucose, liver and renal function tests, vitamin B12, vitamin E, folic acid, autoimmune antibodies, and infection including hepatitis virus antibodies, Treponema serology, HIV antibodies). Cerebrospinal fluid examination showed a normal opening pressure, the cell count, protein, glucose, IgG index, anti-aquaporin-4 antibody, and intrathecal IgG synthesis rate without oligoclonal bands.